1. Field of the Invention
The present invention relates to a control apparatus and method for use in an air conditioning system. More specifically, this invention concerns providing failsafe supplemental heat operation with a microprocessor control for an air conditioning system.
2. Description of the Prior Art
Various sources of heat energy may be utilized to provide space conditioning. Fossil fuel fired furnaces, electric resistance heat and reversible refrigeration circuits are all well known for utilization for space heating. In a typical system a thermostat is provided to sense the temperature of the space to be conditioned and means are provided for energizing the heat source in response to the temperature detected.
In many reversible refrigeration circuit or heat pump systems multiple heat sources are utilized. In a typical system a heat pump may be utilized under certain conditions to supply heat energy to the space and under other conditions backup or supplemental heating means may be utilized for supplying heating to the space. The backup supplemental heating in these conditions may be electric resistance heat connected to supply heat energy in combination with the heat pump or in addition thereto. Other types of supplemental heat may include a fossil fuel fired furnace which would be operated and the heat pump operation discontinued such that the separate heat sources would not operate simultaneously.
It has also been known in the air conditioning field that heat pumps may fail or may operate inefficiently due to some cause. In such event the operator may wish to continue heating of the space without operation of the heat pump. Under such conditions it has been known to utilize a supplemental heat switch for placing the system in supplemental heating operation. Typically, supplemental heat operation has been the energization of backup electric resistance heat associated with the heat pump.
The present invention concerns the utilization of a microprocessor control in combination with a space conditioning system. Power is supplied to the control through the thermostat. The thermostat is arranged such that, should a supplemental heating need be ascertained, operation of the heating system in the supplemental heating mode may be accomplished by throwing a manual switch on the thermostat which acts to discontinue power to the microprocessor control. The present invention provides for the microprocessor being arranged such that should operating power to the microprocessor be discontinued then, in that event, the appropriate connections will be made through the microprocessor control to energize the supplemental heat in response to a first stage heating need being detected by the thermostat.